Tip propelled device for motion through a passage

ABSTRACT

A self-propelled device for locomotion through a lumen, comprising a set of serially arranged inflatable chambers, the end ones of which expand at least radially when inflated. Connecting passages provide fluid communication between each pair of adjacent chambers. A fluid source is attached to one of the end chambers. The connecting passages are such that the fluid inflates the chambers in a sequence, beginning with the chamber closest to the source, and ending with the chamber furthest from the source. The same sequence occurs when the chambers deflate, beginning with the chamber closest to the source, and ending with the chamber furthest from the source. The fluid source can either be a fluid supply tube, extending to a supply outside the lumen, or it can be built-in and carried by the device. The device can crawl either along the lumen wall or on an inserted guide wire.

FIELD OF THE INVENTION

The present invention relates to the field of inflatable devices capableof self propelled motion through tubes, especially for endoscopic andvascular use.

BACKGROUND OF THE INVENTION

The ability to crawl through long, flexible, and curved tubes has longbeen a challenge for engineers since numerous applications can benefitfrom a reliable solution. This ranges from medical applications fortreatment and diagnosis to sewer pipes, gas pipes and power plants.

Current solutions often contain a payload such as a camera, that ispushed from the back by a long flexible rod or wire. This is thesolution currently used in most medical applications with guide wires orcatheters as used to deliver diagnosis or treatment instruments to thedesired position, e.g. catheterization, colonoscopy, ureteroscopy,dilating balloon, and others.

In some type of applications it is impossible to push the active headfrom the back because the force required would cause buckling of thelong rod or wire. One of the biggest shortcomings of current endoscopesand catheters is that they are pushed into the human body manually overa curved path, thereby causing friction, and possible injuries to theinner tissue walls of the lumen.

In search for a solution, a number of locomotion types of propulsionhave been developed, which pull at the distal end of the lumen ratherthen pushing at the proximal end. Examples in non-medical applicationsinclude crawling vehicles and spider-like robots, such as are describedin U.S. Pat. Nos. 6,824,510, and 5,090,259. In medical applications themost common solution is that of the inch worm type, that advances bymeans of peristaltic motion, such as is described, for instance, in U.S.Pat. Nos. 6,764,441, 4,176,662, 5,090,259, 5,662,587, 6,007,482 and5,364,353, and in the article by P. Dario, et al., “Development and invitro testing of a miniature robotic system for computer-assistedcolonoscopy,” published in Computer Aided Surgery, Vol. 4, pp. 1-14,1999, and in the article “A Locomotive Mechanism for a RoboticColonoscope” by Byungkyu K, et al., published in Proceedings of theIEEE/RSJ Intl. Conference on Intelligent Robots and Systems; 2003, pp.1373-8. Another type of medical application device is described in U.S.Pat. No. 6,702,735.

Another solution is one which imitates the locomotion of the earth-worm(Annelida), that generates waves of contraction and relaxation ofalternate muscle groups (longitudinal and circular muscles), causing theworm to move forward, such as is described in the article by J. Dietrichet al., entitled “Development of a peristaltically actuated device forthe minimal invasive surgery with a haptic sensor array” published inMicro- and Nanostructures of Biological Systems, Halle, Shaker-Verlag,69-88. ISBN 3-8322-2655-9. Another solution suggested uses motionhydraulically generated close to the tip, such as is described in U.S.Patent Application 2005/0033343, for “Catheter Drive” to I. Chermoni.

Most of the above described devices have the disadvantage that a numberof control lines or pneumatic tubes are required to operate the device,which complicates both the control system and the physical deployment ofthe device within the passageway. The device described in theabove-mentioned U.S. Pat. No. 5,364,353 for “Apparatus for advancing anobject through a body passage” to M. T. Corfitsen et al., on the otherhand, requires only one inflation tube. In this patent, there isdescribed a device using a single bladder and an axially expandablebellows with a throttle valve between them. A tube is provided with alumen for the supply and removal of inflation medium to the bladder andbellows. The throttling valve ensures that the inflation of the bladderis delayed relative to the axial expansion of the bellows as pressure isapplied to the inflation tube, and that the deflation of the bladder isdelayed relative to an axial contraction of the bellows as pressure isreleased from the inflation tube, such that the device can be advancedstepwise through, for instance, a gastrointestinal canal.

However, the device described in U.S. Pat. No. 5,364,353 has a drawback,which may make it problematic for use in real life situations. Thedevice moves forward by means of axial expansion of the bellows sectionfollowed by radial anchoring of the bladder section against the insideof the passageway being negotiated, and then pulling forward of thebellows section and its trailing inflation tubes while the bladder isstill anchored by its inflation pressure. However, during the forwardcreeping stage of the bellows, the applicants state that the device usesthe bends in the trailing inflation tube to provide the friction andhence the resistance against which the device is pushed forward, thisbackward resistance preventing the inflation tube from being pushedback, and ensuring that the device tip moves forward.

However, the very same friction in the trailing tubing used as a rearanchor for the device when moving forward, will tend to prevent thedevice from pulling the trailing tubes forward as the bellows deflates.In order to pull the trailing tubing forward, the front bladder of thedevice presumably needs to grip the internal passageway strongly, whichmay not be desirable in some cases. In order to overcome reliance on therearward friction as described in U.S. Pat. No. 5,364,353, such a deviceshould therefore have some additional mechanism that anchors the devicein place during the inflation phase.

Most of the above described devices therefore appear to have variousdisadvantages which limit their usefulness in one aspect or another,such that there is need for a new, distally propelled catheter headwhich can operate simply, over long tracts of internal passages, andwithout causing undue damage to the inner walls of the passages.

The disclosures of each of the publications mentioned in this sectionand in other sections of this application, are hereby incorporated byreference, each in its entirety.

SUMMARY OF THE INVENTION

The present invention seeks to provide a new method and device forself-propulsion along internal passageways, having a simple controlsystem requiring only a single inflation and deflation cycle to propelthe device. The device utilizes the dynamic behavior of fluid connectedinflated balloons, whereby a time delay in the passage of inflatingfluid from rearmost to foremost balloon is utilized to inflate theballoons in sequence beginning with the rearmost, and ending with theforemost. Conversely, this same time delay ensures that deflation of theballoons also proceeds in sequence beginning with the rearmost, andending with the foremost. The device of the present invention uses aseries of inflatable chambers to make up the traction unit, with thedevice sequentially gripping preferably the inside wall of thepassageway with the chamber or chambers disposed at the rear or proximalend of the series while the device expands forward with inflation of theother chambers, and then gripping preferably the inside wall of thepassageway with the chamber or chambers situated at the front or distalend of the series, while the device pulls up its rear end with deflationof the other chambers. By this means, no reliance is necessary on thephysical situation present in the rearward tract of the passageway toprovide backward frictional resistance to the trailing inflation tube,and the trailing tube can be made of a highly flexible and resilientmaterial, such that it causes no friction or damage to the passagewaybeing traversed. At the same time, the radial pressure which needs to beapplied to the inside walls of the passageway being negotiated isminimal, since there is minimal trailing friction to overcome.Furthermore, according to further preferred embodiments of the presentinvention, in which the fluid source is not supplied by means of asupply tube, but is provided on board, the device is able to operateindependently of its mechanical surroundings.

The device is operable with a series of only two inflatable chambers,each of which expands radially and axially when inflated, but the use ofmore than two chambers may have an advantage in that the radial pressureon the walls is spread out over more chambers, thus reducing theinternal pressure required to anchor the relevant chambers of thedevice. Furthermore, the use of a larger number of chambers may enablelarger payloads to be transported or pulled by the device.

The device of the present invention has a number of other advantages,either alone or in combination, over prior art devices:

(i) The device itself may be completely passive, and does not need toincorporate any actuators, engines, valves or electrical controllers onboard. If required, such components may be located remotely from thedevice outside of the body. For those preferred embodiments where thedevice is autonomous, or untethered, such components may then be mountedon-board.(ii) It may be fabricated from flexible materials only, to enable easyaccess to most interior cavities, and, when used in medicalapplications, to ensure minimum injuries and trauma to the inner tissuesof the passageways of the subject.(iii) It has only a single supply line, to enable a small, flexible andlow-drag “tail”. Additional tubes may be added to provide specialfunctions, unrelated to the motive aspects of the device, such as theinjection of medication at the device tip, or an X-ray opaque medium.(iv) Lack of inflation of one or more sections, for instance due to anarrow section of the passageway, does not stop the device fromfunctioning. The following balloons will receive the required fluidsupply in that case.(v) The propulsion system applies itself to the interior wall of thepassageway or cavity over a large area and preferably covering severalcells, thereby reducing the forces applied on the tissue, and reducingpotential injury thereto.(vi) The system can be constructed is such a way that keeps the innerlumen free for insertion of an endoscope, guide wires, and othersurgical tools.(vii) The balloons can be distributed along a long length of thepassageway, so the propulsion effect is distributed along a long regionof the passageway. This, for example, allows use in the intestine or anyother long curved passageway.(viii) The annular structure of the balloon enables the device to bedesigned such that its gripping pressure is applied to an inner guidewire, and the unit advances by “creeping” along this guide wire. In thisway, motion can be achieved without the application of pressure to theouter wall of the passageway. This may be important, for example, toavoid applying pressure to unstable coronary plaques, or to prevent harmthe inner walls.

The device according to the present invention is particularly useful inmedical applications for self-propulsion of a catheter through a lumen,by its tip. It can be applied in various medical fields such asEndoscopy, Gastro-entereology, Urology, Cardiology, Cochlearimplantation, sub-dural spinal applications, and others. Although theinvention is generally described in this application in terms of itsmedical application, it is to be understood that the invention is alsoequally applicable to non-medical applications, where vision,accessibility or maintenance are needed in passageways, such as inindustrial plant, gas pipes, power plants, tunnels, utility pipes, andthe like.

There is thus provided in accordance with a preferred embodiment of thepresent invention, a a self-propelled device for locomotion through alumen, comprising:

(i) a set of serially arranged inflatable chambers, comprising:

(a) at least a first and a second chamber expanding at least radiallywhen inflated,

(b) at least a third chamber disposed between the at least first andsecond chambers, the third chamber expanding at least axially wheninflated, and

(c) at least one connecting passage providing fluid communicationbetween each pair of adjacent chambers, and

(ii) a fluid source attached to one of the chambers located at a firstextremity of the set of serially arranged inflatable chambers,wherein the connecting passages are adapted such that fluid from thesource inflates the set of serially arranged inflatable chambers in asequence, beginning with the inflatable chamber closest to the fluidsource, and ending with the inflatable chamber furthest from the fluidsource.

The fluid source may preferably comprise a fluid supply tube, which maythen be adapted to be supplied with the fluid externally to the lumen,or it may comprise a pumping system attached to the device and drawingfluid from the lumen, or it may comprise a closed circuit containing thefluid and attached to the device.

In any of the above-mentioned devices, the set of serially arrangedinflatable chambers also deflate in a sequence, beginning with theinflatable chamber closest to the supply tube and ending with theinflatable chamber furthest from the supply tube, when the fluid flowsout of the set of serially arranged inflatable chambers.

Furthermore, the at least first and second chambers may also preferablyexpand axially when inflated, and the at least third chamber may alsopreferably expand radially when inflated.

In accordance with yet another preferred embodiment of the presentinvention, in any of the above-described devices, at least the first andthe second inflatable chambers are adapted to grip the wall of the lumenon expanding radially. Furthermore, the above-described devices are suchthat the device moves along the lumen as the chambers inflate anddeflate sequentially.

There is further provided in accordance with yet another preferredembodiment of the present invention, a self-propelled device asdescribed hereinabove, and wherein at least one of the radiallyinflatable chambers comprises an outer skin having at least onelongitudinal section of greater rigidity than other sections of theouter skin, such that when the at least one chamber inflates, thelongitudinal skin section of greater rigidity does not touch the wall ofthe lumen. According to another preferred embodiment of the presentinvention, the at least one longitudinal skin section is disposedasymmetrically around the circumference of the axis of the chamber, suchthat when the chamber inflates, it generates a bend in the axis of theset of serially arranged inflatable chambers.

In accordance with still another preferred embodiment of the presentinvention, there is provided a self-propelled device according to any ofthe above described embodiments, and further comprising at least onetubular chamber disposed between the fluid source and the chamber towhich the fluid source is attached, and in fluid contact with both, thetubular chamber being adapted to inflate radially so as to applypressure to the lumen walls, and a pressure operated valve which closeswhen a predetermined pressure higher than that required to inflate theset of chambers, is applied thereto, the pressure operated valve beingdisposed between the tubular chamber and the set of chambers, such thatthe set of chambers are isolated from pressure applied to inflate thetubular chamber.

There is further provided in accordance with still another preferredembodiment of the present invention, any of the above describedself-propelled devices may further comprise a tapered tip attached to asecond extremity of the set of serially arranged inflatable chambers,opposite to the first extremity attached to the fluid source, such thatthe tip proceeds the device as it moves along the lumen. The tapered tipmay preferably be made inflatable, and in fluid connection with theinflatable chamber at the second extremity, such that the tip inflatesafter the inflatable chamber at the second extremity. Alternatively andpreferably to the provision of a tip, any of the above describedself-propelled devices may further comprise a drilling head attached toa second extremity of the set of serially arranged inflatable chambersopposite to the first extremity attached to the fluid source, such thatthe drilling head proceeds the device as it moves along the lumen. Thedrilling head is preferably powered by either the inflating fluid, or byan electric motor or by a rotating guide wire.

In accordance with yet another preferred embodiment of the presentinvention, there is provided a self-propelled device for locomotionthrough a lumen, comprising:

(i) a set of serially arranged inflatable chambers, and(ii) a system supplying fluid to the set of serially arranged inflatablechambers, such that the fluid inflates the set in a serial sequence,from one end to the other end,wherein at least one of the inflatable chambers comprises an outer skinhaving at least one longitudinal section of greater rigidity than othersections of the outer skin, such that when the at least one chamberinflates, the rigid longitudinal skin section does not touch the wall ofthe lumen. In this case, according to a further preferred embodiment,all of the at least one longitudinal skin sections are disposedasymmetrically around the circumference of the axis of the chamber, suchthat when the at least one chamber inflates, it generates a bend in theaxis of the set of serially arranged inflatable chambers.

There is further provided in accordance with yet another preferredembodiment of the present invention, a self-propelled device forlocomotion through a lumen, comprising:

(i) a set of serially arranged inflatable chambers,(ii) a system supplying fluid to the set of serially arranged inflatablechambers, such that the fluid inflates the set in a serial sequence,from a first end of the set to its opposite end, and(iii) an obstruction clearing tip attached to the set at the oppositeend.The obstruction clearing tip may preferably be a tapered tip, or adrilling head, such that the drilling head proceeds the device as thedevice moves along the lumen.

In accordance with still another preferred embodiment of the presentinvention, there is also provided a self-propelled device for locomotionthrough a lumen, comprising:

(i) a set of serially arranged inflatable chambers,(ii) a system supplying fluid to the set of serially arranged inflatablechambers, such that the fluid inflates the set in a serial sequence,from one end to the other end, and(iii) a hollow passageway running through the central region of thechambers, such that the chambers inflate annularly around thepassageway. In such an embodiment, the walls of the chambers surroundingthe hollow passageway may preferably have a rigidity such that thehollow passageway is not compressed by the chambers when inflated. Insuch a case, the central passageway may be adapted to contain a threadedelement along at least part of its length, the element being unattachedto the self-propelled device.

Alternatively and preferably, the walls of the chambers enclosing thehollow passageway may apply pressure to the hollow passageway when thechambers are inflated. In such a case, the central passageway may besuch that the chambers grip the threaded element when inflated.Additionally, the chambers may have an external diameter such that theydo not grip the lumen when inflated. In this case, the device preferablymoves along the threaded element as the chambers inflate and deflatesequentially.

In either of the above two central passageway embodiments, the threadedelement may preferably be any one of a guide wire, an optical fiber or alength of tubing.

There is further provided in accordance with still another preferredembodiment of the present invention, a method of characterizingparameters relating to the walls of a lumen using any of the abovedescribed self-propelled devices, comprising the steps of:

(i) inserting the device into the lumen,(ii) monitoring the supply pressure of the fluid as the chambers inflatesequentially,(iii) determining which chamber of the set is being inflated as afunction of time by observing changes occurring in the supply pressure,(iv) monitoring the fluid flow into the set of chambers, such that theinflation volume of each chamber is known by use of the results of step(iii), and(v) determining the internal diameter of the lumen at the position ofeach chamber from the inflation volume determined in step (iv).

This method may also preferably comprise the additional step ofcorrelating the inflation pressure build-up and the flow rate into eachchamber with predetermined relationships between the measurements andthe wall compliance, such that the wall compliance of the lumen at thelocation of each chamber may be determined.

In accordance with a further preferred embodiment of the presentinvention, there is also provided a method of inserting a guide wirethrough a lumen, using one of the above-described devices having ahollow passageway running through the central region of the chambers,comprising the steps of:

(i) inserting the guide wire a predetermined distance into the lumen,(ii) inserting the device into the lumen such that it rides of the guidewire,(iii) moving the device through the lumen by sequential inflation of itschambers, until it envelops the tip of the guide wire,(iv) advancing the guide wire a further predetermined distance into thelumen, and(v) repeating steps (iii) and (iv) until the device reaches its target.

In such a method, the walls of at least some of the chambers surroundingthe hollow passageway have a rigidity such that the hollow passageway isnot compressed by the chambers when inflated, such that the device movesthrough the lumen by gripping the walls of the lumen. Alternatively andpreferably, the walls of at least some of the chambers enclosing thehollow passageway do apply pressure to the hollow passageway when thechambers are inflated, such that the device moves through the lumen bygripping the guide wire.

There is even further provided in accordance with another preferredembodiment of the present invention a self-propelled device forlocomotion through a lumen, comprising:

(i) a set of two inflatable chambers, both of which expand radially wheninflated and at least one of which also expands axially when inflated;(ii) at least one connecting passage providing fluid communicationbetween the two chambers, and(iii) a fluid source attached to one of the chambers,wherein the at least one connecting passage is adapted such that fluidfrom the source inflates the two inflatable chambers in a sequence,beginning with the inflatable chamber closest to the fluid source, andending with the inflatable chamber furthest from the fluid source.

In this preferred embodiment, the two inflatable chambers preferablyalso deflate in a sequence, beginning with the inflatable chamberclosest to the fluid source and ending with the inflatable chamberfurthest from the fluid source, when the fluid flows out of the twoinflatable chambers.

In any such embodiment, the fluid source may preferably comprise a fluidsupply tube, which may then be adapted to draw the fluid from a supplyexternal to the lumen, or it may comprise a pumping system attached tothe device and drawing fluid from the lumen itself, or it may comprise aclosed circuit containing the fluid and attached to the device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 illustrates schematically a tip-propelled catheter device,constructed and operative according to a first preferred embodiment ofthe present invention;

FIGS. 2A to 2I illustrates schematically how the fluid inflates theballoon cells of the device of FIG. 1 in a sequence that causes thedevice to move forward;

FIG. 3A illustrates schematically a method of manufacturing the deviceof FIG. 1 using separate joined segments while FIGS. 3B and 3Cillustrate further preferred embodiments of the device of FIG. 1 inwhich the fluid supply system is packed on board the device, thusproviding an untethered device without a trailing fluid supply line;

FIGS. 4A and 4B illustrate schematically a preferred embodiment of thedevice of FIG. 1, incorporating a passage for a central tube;

FIGS. 5A to 5D illustrate schematically a further embodiment, whichenables blood or another fluid to flow around the balloons of thedevice;

FIGS. 6A to 6C illustrate schematically an embodiment in which some ofthe balloons in the device inflate and expand only axially, like abellows;

FIGS. 7A to 7C illustrate schematically an embodiment in which thedevice is constructed of one piece of flexible material with integralpartitions and metal inter-balloon orifices;

FIGS. 8A and 8B illustrate an embodiment similar to that of FIGS. 7A to7C, but with the orifices formed in the material of the separator walls;

FIG. 9 illustrates schematically an embodiment showing a “Multiple PointDrive” device enabling driving forces to be deployed along the wholedevice, which can thus be made longer than otherwise;

FIGS. 10A and 10B illustrate schematically an embodiment similar to thatof FIG. 9, but with an inflatable straight section operative as adilator;

FIGS. 11A to 11C illustrate schematically an embodiment of the presentinvention, which is able to turn or navigate round bends in the passagebeing negotiated;

FIGS. 12A and 12B illustrate schematically an embodiment in which thelocking occurs on an inside tube or guide wire;

FIGS. 13A to 13C illustrate schematically an embodiment having a taperedtip able to force its way through partial blockages encountered;

FIG. 14 illustrates an embodiment in which a turbine head is fitted tothe front of the device, for burrowing its way through obstructionsencountered;

FIGS. 15A to 15C illustrate embodiments of the present invention, inwhich the device is utilized to determine parameters relating to thewalls of a passageway negotiated by the device, such as internaldiameter, and wall compliance; and

FIG. 16 illustrates schematically an embodiment in which the device isused in a novel steering system in coordination with an internalsteerable guide wire, the device being propelled on the guide wire orthe outer walls of the passageway.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which illustrates schematically atip-propelled catheter device 15 for traveling down a lumen 10,constructed and operative according to a first preferred embodiment ofthe present invention. The device preferably comprises a number ofballoons 11 connected to each other by separators 12 with one or moresmall openings, preferably in the form of orifices 13 formed therein,such that all the balloons comprise a single volume. For ease ofconstruction, the device can alternatively and preferably comprise asingle inflatable balloon divided into separate balloon segments byseparators with orifices such that the entire segmented balloon can beinflated through a single input. The balloon fabric is preferably heldin place relative to the separators 12 by means of rings 17 or glued ormolded to the separators. Whichever preferred construction is used, thedevice is connected by a single tube 16 to a fluid supply for inflatingthe balloons or the balloon segments. For the sake of simplicity, theoperation of the device will be explained using the term balloon foreach separate segment, although it is to be understood that theinvention can equally be implemented using a single balloon segmented toform the separate segments. The inflation fluid used can be any one of acompatible gas or liquid.

According to a further preferred embodiment of the present invention,the fluid supply can be taken from the passageway through which thedevice is moving, by means of an on-board pump, and ejected theretoafter use, as more fully described hereinbelow.

Reference is now made to FIGS. 2A to 2I which illustrates schematicallyhow the fluid inflates the balloon cells in a sequence that causes theproximal one to inflate first, increasing its diameter as well as itslength. Being inflated, it locks itself against the inside walls of thetube, but at the same time, its increase in length advances the othercells which are not fully inflated yet and hence are not locked on theinside walls of the tubes. The cell are inflated in a sequence until thedistal cell locks against the inner tube walls, but at a positionfurther along the tube than that of the un-inflated balloon distal cellinitial position. This situation is reached in FIG. 2E. The timing andorder of the sequence is mandated by the fluid flow dynamics through theorifices, and the dynamics of the balloon inflation. Disconnecting thesupply and allowing the fluid pressure to drop at this point, or pumpingout the fluid, as shown in FIG. 2F, causes the proximal cell to deflatefirst reducing both its length and diameter. Since the distal cell andall of the intermediary cells, are at this point still fully inflated,they are still locked against the inner walls of the tube, thus pullingthe proximal cell inward as the balloon deflates and decreases itslength.

The sequential motion series is repeated inducing motion of the entiredevice as can be seen in FIGS. 2A to 2I. The locomotion sequence iscomposed of two phases: inflation and deflation, with the arrows at theentrance of the inflation tube indicating the direction of fluid flow.The dynamics of the sequential inflation is as follows:

The flow through an orifice is proportional to the square root ofpressure difference across the orifice, and the square of the diameterof the orifice, such that the orifice sizes can be selected to providespecific inflation dynamics.

Inflation phase: Initially, the pressure is equal in each balloon and isequal to the outside pressure, therefore the balloons are in deflatedcondition, as in FIG. 2A. When the pressure in the supply tube rises,the fluid begins to flow through the first orifice into the first(proximal) balloon, as in FIG. 2B. The pressure difference between thefirst and second balloons is now lower than the pressure differencebetween the supply tube and the first balloon, such that the flow ratein the second orifice is slower and the second balloon inflates moreslowly than the first one. By this means, the pressure propagates in acontrolled and gradual manner to the last (distal) balloon until thepressure in all the balloons is equal, as shown in FIG. 2E.

Deflation phase: Now the pressure in the supply tube is reduced to theoutside pressure, or the fluid is pumped out of the inflation tube, andthere is then a pressure drop between the supply line and the firstballoon. The fluid begins to flow out of the first balloon, as in FIG.2F. Again, since the pressure difference between the supply tube and thefirst balloon is greater than between the rest of the balloons, thefirst balloon deflates first, then deflates the second, and so on untilthe last balloon is deflated, as in FIG. 2I.

In a variation of the actuation sequence, it is possible to initiate thecycling process even before the last cell is fully deflated. In such acase there will always be a base point anchored to the passageway andhence will prevent unwanted slippage in the case of external forces.Furthermore, different orifices sizes, or different numbers of orifices,can be used between different positioned balloons to improve thelocomotion and speed of the device, all according to the dynamics of thefluid flow in to, out of, and between balloons. Furthermore, theviscosity of the inflation fluid can be chosen to improve the locomotiondynamics.

Reference is now made to FIG. 3A which illustrates schematically analternative and preferred method of manufacturing the device, in whicheach section 31 is manufactured separately and sections are connected byseparators 30 which act as clips for the balloon segments, with orwithout glue. Throughout this application, the use of the terms set orseries of chambers which make up the structure of the device of thepresent invention, are understood to be applicable, and are thuswiseclaimed, whether the chambers are separate structural segments connectedtogether, as shown in the preferred embodiment of FIG. 3A, or whetherthey are constructed of a single one piece structure separated intoseparate chambers by means of mechanical partitions, as shown in thepreferred embodiment of FIG. 1.

According to the above-described embodiments of the present invention,the supply line is attached externally to a fluid supply, and itscontrol system, this being known as a tethered application. According tofurther preferred embodiments of the present invention, schematicallyillustrated in FIGS. 3B and 3C, the fluid actuation system can be packedon board the device, thereby obviating the need for a supply line to theoutside. In the embodiment of FIG. 3B, a pump 35 is located on thedevice, pumping in the fluid through an opening 36 from its surroundingenvironment within the passageway, and expelling the fluid thereto also.If the device is operating, for example, in the vascular system, thefluid used is blood; if in a gas pipe, for example, it can use the gasto inflate and deflate the balloons; if in a regular tunnel or pipe, thefluid is the air within that tunnel or pipe. The actuation system canhave an internal power source preferably in the form of a battery, or anexternal power source, such as an induced electro magnetic field or anyother kind of induced power source. The device then moves forwardunattached to any fluid supply line and solely under the control ofcommands transmitted to it from the outside.

Alternatively and preferably, in a different untethered embodiment, asillustrated schematically in the embodiment of FIG. 3C, the inflatingfluid is in the form of a gas, and is supplied to the inflatableballoons from an on-board reservoir 33 of the compressed gas. Theinflation gas is therefore contained in a closed circuit, isolated fromthe fluid of the surrounding environment, and is returned to thereservoir 33 when the balloons are deflated, preferably by means of asmall recycling compressor 34. The inflation fluid can then be of anysuitable type of gas, independent of the fluid flowing through thepassageway.

Reference is now made to FIGS. 4A and 4B which illustrate schematicallya further preferred embodiment of the present invention, in which acentral passage 49 has been incorporated into the device, preferablyrunning through the central region of each of the balloons and theseparators. The orifices 43 for the sequential pressure regulation arethen offset in the separator walls 42. The central passage can be usedfor inserting an optional optical fiber, a guide wire, electronic leadsto a camera mounted in the nose of the device, or similar. Although notapparent because of the scale of the drawing of FIGS. 4A and 4B, thecentral passage is of such a size that there is a small space betweenthe inner surface 49 of the balloons and the internally inserted wire orother internally threaded item 48, so that the wire or other item canmove freely through the device. In the embodiment of FIG. 4B, an innerspring 47 has been added to the structure to support the inner tube 49from collapsing on the guide wire 48 or other internally threaded item,and locking the tube onto it, when the balloon is inflated.Alternatively and preferably, the central passage can be used to allow acontinuous flow of blood or other vital fluid through the lumen beingnegotiated by the device, so that the balloons of the device do notblock such flow.

FIGS. 4A and 4B describe the incorporation of a central passage forthreading wire-like elements in a self-propelled locomotion device ofthe type of the previously mentioned embodiments of FIGS. 1 to 3 of thepresent invention. However, it is to be understood that the centralpassage described in the embodiments of FIGS. 4A and 4B, and thebenefits arising therefrom, can also be advantageously incorporated inany of the prior art inflatable chamber self-propelling devices, and thepresent invention is meant to include also such embodiments.

Reference is now made to FIGS. 5A to 5D which illustrate schematically afurther preferred embodiment of the present invention, which enablesblood or another fluid to flow around the balloons 51. This is useful inlocomotion along arteries or tubes 50 where the fluid flow can not bestopped by the presence of the device, and bypasses are required.According to this embodiment, the balloons are constructed such thatthey do not have a circular shape when inflated. A longitudinal sectionof the outer skin of the balloon is constructed to be less flexible thanthe rest of the outer skin, preferably by the addition of longitudinalreinforcing strips 53 along the balloon length, such that the balloondoes not expand to its full size, if at all, along these sections. FIG.5B illustrates schematically a cross section of an uninflated balloon,while FIG. 5C shows an inflated balloon, showing the clear regions 59through which the body fluid flow can continue uninterrupted. FIG. 5Dshows an isometric view of the device with one balloon inflated.

FIGS. 5A to 5D describe the incorporation of a fluid bypass section inthe balloons of a self-propelled locomotion device of the type of thepreviously mentioned embodiments of the present invention, using serialchambers with automatic inflation sequencing. However, it is to beunderstood that the fluid bypass section described in the embodiments ofFIGS. 5A to 5D, and the benefits arising therefrom, can also beadvantageously incorporated in any of the prior art inflatable chamberself-propelling devices, and the present invention is meant to includesuch embodiments also.

Reference is now made to FIGS. 6A to 6C which illustrate schematically afurther preferred embodiment of the present invention, in which some ofthe balloons in the device are constructed to inflate and expand onlyaxially, like a bellows, thereby providing a longer reach per motioncycle. In the preferred embodiment of FIG. 6A, balloons 61A and 61C areregular balloons which expand radially and axially when inflated, asshown in FIG. 6B, such that they perform the wall gripping functions ofthe device, while balloons 61B and 61D have reinforcing rings 62 builtinto their envelope, such that when they inflate, as shown in FIG. 6C,they generate significant axial expansion but little if any radialexpansion.

Reference is now made to FIGS. 7A to 7C which illustrate schematically afurther preferred embodiment of the present invention, in which thedevice is constructed of one piece of flexible material with integralpartitions 72 at the balloon segment dividers, and metal jet structures70 inserted into the centers of these partitions to act as the orificesbetween successive balloon chambers 71. Such construction reduces themanufacturing costs of the device. Alternatively and preferably, amultiple orifice insert can be used.

Reference is now made to FIGS. 8A and 8B which illustrate schematicallya further preferred embodiment of the present invention, similar to thatof FIGS. 7A to 7C, except that the orifices themselves 83 are formed inthe material of the separator walls 82, thereby lowering constructioncosts even more. The material between sections is preferably made wideror stiffer to keep a constant orifice diameter. The supply pipe 86 canalso preferably be manufactured as part of the same piece of material.

Reference is now made to FIG. 9 which illustrates schematically afurther preferred embodiment of the present invention, showing a“Multiple Point Drive” device. Groups 95 of driving balloons 91, or evenindividual driving balloons 91 can be separated with non inflatabletabular sections 94. This enables driving forces to be deployed alongthe whole device, resulting in a better traction and higher stroke perinflating sequence. This is very useful for moving through very long andcurved passages, such as arteries or intestines or the like in medicalapplications. The device operates as a very long inchworm withpropulsion forces along the whole body. An advantage of this embodiment,or of any embodiment using balloons over the complete length, over anembodiment using balloons only at the tip is that the crawling speed ishigher since the effective stroke length is longer, and the pressure isdistributed more evenly along the inner walls.

Reference is now made to FIGS. 10A and 10B which illustrateschematically a further preferred embodiment of the present invention,which has some similarities to that of FIG. 9, except that the straightsections 109 are constructed of a material that does inflate under apredefined pressure. The balloon section 104 is propelled as explainedabove. A pressure valve 103 is built into the entrance to the balloonsection 104, and is adapted to close when the pressure 106 is raised tosome higher value than that used during normal inflation operation ofthe balloon propulsion section 104.

This increased pressure can be used for expanding the straight chamber109 of the device, which thus acts as a dilator section 105, availablefor producing therapeutic effects, without the increased inflationpressure damaging the balloon propulsion units. When the balloonpropulsion units 104 have brought the device to its desired targetposition, the pressure 106 is increased, the valve 103 closes and thedilator 105 can be inflated with high pressure to perform its desiredfunction. The valve 103 keeps the high pressure 106 out of thepropulsion balloons. Alternatively and preferably, if the propulsionballoons 104 are made in such a way or of such a material that theirinflation is limited, then no valve 103 is required.

When the therapeutic procedure is complete, pressure is lowered, thevalve 103 opens again, and the device can again be operated normally.The high pressure can be used to open a partially blocked artery forexample, or for expanding a stent located in its collapsed state overthe section 105, or for injecting a drug from the device into thepassageway being traversed, or for any other action requiring theapplication of a localized mechanical pressure.

The fluid supplied for propulsion can preferably be an X-Ray opaquefluid, so that it will be possible to observe the device using X-Rayimaging during insertion and propulsion.

Reference is now made to FIGS. 11A to 11C which illustrate schematicallya further preferred embodiment of the present invention, in which areinforced area, preferably in the form of one or more strips 112, hasbeen provided asymmetrically in the outer skin or wall of one or more ofthe balloons 111. When a balloon with such a reinforced area isinflated, the region where the reinforcement is located is not able tostretch in the same way as the other regions of the balloon, and abending effect is generated, which can be used for turning or navigationof the device when a bend or a junction 115 in the lumen is reached, asin FIG. 11B. Such reinforcing strips can equally well be added tosuccessive balloons of the device in order to generate a more gradualturn along the length of the device.

FIGS. 11A to 11C describe the incorporation of a reinforced section forgenerating a turning effect in the balloons of a self-propelledlocomotion device of the type of the previously mentioned embodiments ofthe present invention, using serial chambers with automatic inflationsequencing. However, it is to be understood that such a reinforcedsection for generating a turning effect as described in the embodimentsof 11A to 11C, and the benefits arising therefrom, can also beadvantageously incorporated in any of the prior art inflatable chamberself-propelling devices, and the present invention is meant to includesuch embodiments also.

Reference is now made to FIGS. 12A and 12B which illustrateschematically a further preferred embodiment of the present invention,in which the locking occurs on an inside tube or guide wire 128. This isaccomplished by making the outer surface of the balloon stiffer than theinner surface, either by using an intrinsically stiffer material for theouter skin, or, as shown in FIGS. 12A and 12B, by incorporatingreinforcing ribs 121 in the outer wall. In FIG. 12A showing the balloonsuninflated, though not visible in the drawing, there is a small gapbetween the inner passage of the balloons and the internally insertedtube or guide wire 128, so that the tube or wire or other threaded itemcan move freely through the uninflated device. As the balloons areinflated, the inner surface expands inwards, and eventually locksagainst the inner guide wire or tube, as shown in FIG. 12B. The innersurface of the balloons may preferably be fitted with fins 129, so thatthe balloon grips the inner tube or guide wire at narrow points, therebyincreasing the pressure of the grip. Since the central axis of thedevice is occupied by the central tube or guide wire, the orifices 124connecting the various balloons have to be offset from the center.Alternatively and preferably, a number of orifices can be used spreadangularly around the central tube. As with the previous embodiment ofFIGS. 6A to 6C, some of the sections can have essentially circularballoons, and other sections can be cylindrical axially extendingballoons.

FIGS. 12A and 12B describe the incorporation of a central passage forthreading wire-like elements in a self-propelled locomotion device ofthe type of the previously mentioned embodiments of the presentinvention, using serial chambers with automatic inflation sequencing.However, it is to be understood that the central passage described inthe embodiments of FIGS. 12A and 12B, and the benefits arisingtherefrom, can also be advantageously incorporated in any of the priorart inflatable chamber self-propelling devices, and the presentinvention is meant to include such embodiments also.

Reference is now made to FIGS. 13A to 13C which illustrate schematicallya further preferred embodiment of the present invention, in which thedevice is provided with a tapered tip 138 which, as the device advancesthrough the passageway, is able to force its way through partialblockages 137 encountered. The tip partially compresses the blockagematerial against the wall of the passageway. Additionally, the devicecan preferably be fitted with a dilator section 136, as in theembodiment of FIGS. 10A and 10B, to complete the operation of clearingthe partial blockage 137.

Reference is now made to FIG. 13D which illustrates schematically afurther preferred embodiment of the present invention, similar to thatshown in the embodiment of FIGS. 13A to 13C, but in which the tip 134 ismade inflatable by means of fluid connection to the most distal balloon.The front end 135 of the tip forces its way into the blockage 137 as thedevice crawls forward, and when the most distal balloon has filled up,the inflatable tip head also inflates, thus packing the blockagematerial against the internal wall of the passageway. Since inflation ofthe tip occurs automatically when the distal balloon has inflated, thisembodiment is simpler than that of FIGS. 10A and 10B, where additionalvalving and pressure monitoring is required.

According to further preferred embodiments of the present invention, inthe arrangements shown in FIGS. 13A to 13D, where only some of theballoons are used for motion purpose, the rest of the balloons and thehead can be used for other therapeutic purposes besides dilation.

Reference is now made to FIG. 14 which illustrates schematically afurther preferred embodiment of the present invention, in which adrilling head 143, such as a turbine or propeller, is fitted to thefront of the device, such that it can burrow its way throughobstructions 147 encountered during its progress down the passageway.The head is preferably hydraulically powered with the power preferablycoming from a paddle 141 or similar, driven by the inflating fluid, orfrom another external hydraulic source. Alternatively and preferably,electric power can be used, which can preferably come from a battery.Alternatively and preferably, the head can be powered from a rotatingguide wire inserted through the center bore of the device.

FIGS. 13A to 13D and FIG. 14 describe the incorporation of various tipembodiments for enabling a self-propelled locomotion device of thepresent invention using serial chambers with automatic inflationsequencing, to force its way through partial blockages encountered inits path. However, it is to be understood that such tip embodiments asdescribed in the embodiments of 13A to 13D and FIG. 14, and the benefitsarising therefrom, can also be advantageously incorporated in any of theprior art inflatable chamber self-propelling devices, and the presentinvention is meant to include such embodiments also.

Reference is now made to FIGS. 15A and 15B, which illustrateschematically further preferred embodiments of the present invention, inwhich the device is utilized to determine a number of parametersrelating to the walls of the passageway through which the device passes.In particular, the device is able to provide information regarding thepassageway internal diameter, and the compliance of the passagewaywalls. The device and this method of operating it is thus particularlyuseful for profiling the condition of a subject's blood vessels or anyother passageway at remote locations in his/her body. The device,according to this embodiment, requires the addition of a pressuremonitor at the fluid input, and of a flow meter to determine the volumeof inflation fluid required to fill the balloons of the device.

FIG. 15A illustrates a balloon, in this exemplary case, the proximalballoon 150, of the device of the present embodiment, at three differentpreferred locations along the length of a passageway, which, for thepurposes of illustrating this preferred embodiment, will be regarded asa blood vessel. The blood vessel is shown having varying wallthicknesses, and hence a varying internal diameter. At point P3, theblood vessel inner diameter is large, at point P1 it is intermediate,and at point P2, it is a minimum. Correspondingly, the volume of fluidused to inflate the proximal balloon 150 is larger at point P3, less atpoint P1 and least at point P2. Measurement of the volumes required forinflation enables the blood vessel internal diameter to be determined ateach cyclical point of the progress of the device through the vessel,once an initial calibration process has been performed to relate balloonvolume to blood vessel diameter.

Continuous monitoring of the flow of inflation fluid during sequentialfilling of the balloons of the device enables a determination to be madeof which balloon is being filled as a function of time, since there is anoticeable pressure change as each successive balloon begins to fill up,and monitoring these pressure changes allows the balloon being filled tobe determined. It is thus possible to relate continuous volume andpressure measurements as a function of time, to the particular balloonbeing filled at any time. Since the filling volume is related to theblood vessel internal diameter, it is thus possible to obtain anestimation of this internal diameter at each point along the length ofthe device. This can be repeated at different positions of the device asit progresses along the vessel, such that a complete diameter profile ofthe blood vessel may be obtained. This is illustrated in FIG. 15B, whichis a schematic graph showing a plot of the inflation volume V, asdetermined from the flow rate into the device, as a function of positionalong the device, which itself is determined from the pressure changesnoted as a function of time. Since each inflated balloon volume is afunction of the vessel diameter, d, the ordinate is designated V(d). Asis seen from the graph, a correlation is shown between the inflationvolume of each balloon and the vessel diameter at each point P1, P2, P3.

However, in addition to the use of the filling pressure to ascertainwhich balloon is currently being filled, this pressure can also be usedin order to provide information about the compliance or rigidity of thevessel walls at points along its length. The position is known from theknowledge of which of the balloons is being filled at the time thepressure is measured, as explained above for the volume measurement. Thevessel diameter at each point is also known from the method of FIG. 15B.There is a correlation between the vessel compliance, which is to bedetermined, and the pressure build-up and flow rate which can bemeasured, and hence the vessel wall compliance can be deduced from thecorresponding time history of the pressure build-up and flow rate.Characterizing and calibrating measurements must first be performed inorder to implement this correlation.

Reference is now made to FIG. 16, which illustrates schematically afurther preferred embodiment of the present invention, in which thedevice is used as a novel steering system in coordination with aninternal pre-bent guide wire. In the prior art, steerable internal guidewires are generally used alone for negotiating curved passageways in thesubject's body. However, such a steerable guide wire, in which the tipcan be bent in the direction of a curve in the passageway beingtraversed, has the disadvantages that the tip can cause injury to thetissue of the internal wall of the passageway as it negotiates its waythrough the passageway, as can the trailing guide wire on curves in thepassageway.

According to this preferred embodiment of the present invention, thesteerable guide wire 168 is used as an internal member of the inflatabledevice as shown in the embodiments of FIGS. 4A-4B, or in the embodimentsof FIGS. 12A-12B, where the inflatable device propels itself forward onthe internal guide wire. In FIG. 16, the configuration of FIGS. 4A-4B isused to illustrate this embodiment. The steerable guide wire 168 is keptretracted within the crawling device as it moves forward, except when acurve 162 in the subject's passageway is to be negotiated, or aY-junction is reached when the tip has to be directed to one branch orthe other, in either of which cases the steerable tip 165 of the guidewire is allowed to protrude by a small distance from the front end inorder to direct the front end of the device at the bifurcation. Thesmall protrusion length prevents the tip from damaging the passagewaywall because of the protection of the front balloon surrounding theguide wire tip and keeping it centrally located in the passageway.Alternatively and preferably, the steerable guide wire tip can be leftjust inside the tip of the device, without protruding at all, andsteered from within, such that it directs the tip of the device roundthe curve without becoming exposed at all outside of the device.Progress through the lumen is thus primarily made by the tip of theinflatable device rather than the tip of a guide wire, therebyincreasing the safety of use.

In the embodiments of the present invention using a central guide wire,such as are described in FIGS. 4A-4B and 12A-12B, the guide wire orcentral tube is generally inserted right to the end of the passage to benegotiated, and the device is allowed to crawl along it. However, theremay be difficulties in inserting the guide wire all the way to itstarget, and in the process, the walls may be damaged by the tip, or byfriction from the trailing guide wire, or dangerous plaque may bedislodged unintentionally. According to a further preferred embodimentof the present invention, a method of use of the device is providedwhereby the internal guide wire is first inserted a short distance intothe passageway to be traversed, typically of the order of 5 cm forpassage down a blood vessel, is held in place externally, and theinflatable device is allowed to crawl along the passageway, as describedin the embodiment of FIGS. 4A-4B, towards the tip of the guide wire.When the inflatable device has progressed sufficiently so that thesteerable tip of the guide wire is preferably just enclosed within thedevice, the device is locked against the passage walls, and the guidewire is pushed forward a further short distance into the passage, andagain held in place externally. The inflated device is then deflated tofree it from the passage walls, and is then allowed to crawl forwarduntil it again covers the exposed portion of the guide wire. Thisprocess is repeated until the guide wire reaches its target point. Bythis means, the guide wire is advanced within the passageway largelyprotected by the surrounding inflatable device, such that the likelihoodof damage to the tissues of the passageway is greatly reduced.

As an alternative to the device climbing the walls of the passage, andanchoring itself on the walls as the guide wire is advanced, this methodcan also be used with the embodiment described in FIGS. 12A-12B, inwhich the device climbs along the internal guide wire itself, withoutapplying pressure on the walls. In this case, the guide wire is pushedforward when the device is deflated without it being anchored, with thetrailing inflation tube providing the small amount of resistance to holdthe device in place while the guide wire is being advanced. Once theguide wire has been advanced a small distance, it is held in placeexternally, while the device crawls along it until has covered thatsmall distance, at which point it releases itself from the guide wire,enabling the guide wire to be advanced another small distance, the wholeprocess repeating itself until the target is reached.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

1. A self-propelled device for locomotion through a lumen, comprising: aset of serially arranged inflatable chambers, comprising: at least afirst and a second chamber expanding at least radially when inflated; atleast a third chamber disposed between said at least first and secondchambers, said third chamber expanding at least axially when inflated;and at least one connecting passage providing fluid communicationbetween each pair of adjacent chambers; and a fluid source attached toone of said chambers located at a first extremity of said set ofserially arranged inflatable chambers; wherein said connecting passagesare adapted such that fluid from said source inflates said set ofserially arranged inflatable chambers in a sequence, beginning with saidinflatable chamber closest to said fluid source, and ending with saidinflatable chamber furthest from said fluid source.
 2. A self-propelleddevice according to claim 1 and wherein said fluid source comprises anyone of a fluid supply tube, a pumping system attached to said device anddrawing fluid from said lumen or a closed circuit containing said fluidand attached to said device. 3-5. (canceled)
 6. A self-propelled deviceaccording to claim 1 and wherein said connecting passages are adaptedsuch that said set of serially arranged inflatable chambers also deflatein a sequence, beginning with said inflatable chamber closest to saidsupply tube and ending with said inflatable chamber furthest from saidsupply tube, when said fluid flows out of said set of serially arrangedinflatable chambers.
 7. A self-propelled device according to claim 1 andwherein said at least first and second chambers also expand axially wheninflated.
 8. A self-propelled device according to claim 1 and whereinsaid at least third chamber also expands radially when inflated. 9-10.(canceled)
 11. A self-propelled device according to claim 1 and whereinat least one of said radially inflatable chambers comprises an outerskin having at least one longitudinal section of greater rigidity thanother sections of said outer skin, such that when said at least onechamber inflates, said longitudinal skin section of greater rigiditydoes not touch the wall of said lumen.
 12. A self-propelled deviceaccording to claim 11, and wherein said at least one longitudinal skinsection is disposed on the circumference of the axis of said chamber, ata position such that when said at least one chamber inflates, itgenerates a bend in the axis of said set of serially arranged inflatablechambers.
 13. A self-propelled device according to claim 1 and furthercomprising: at least one tubular chamber disposed between said fluidsource and said chamber to which said fluid source is attached, and influid contact with both, said tubular chamber being adapted to inflateradially so as to apply pressure to said lumen walls; and a pressureoperated valve which closes when a predetermined pressure higher thanthat required to inflate said set of chambers, is applied thereto, saidpressure operated valve being disposed between said tubular chamber andsaid set of chambers, such that said set of chambers are isolated frompressure applied to inflate said tubular chamber.
 14. A self-propelleddevice according to claim 1 and further comprising a tapered tipattached to a second extremity of said set of serially arrangedinflatable chambers opposite to said first extremity attached to saidfluid source, such that said tip precedes said device as it moves alongsaid lumen.
 15. A self-propelled device according to claim 14 andwherein said tapered tip is inflatable, and is in fluid connection withsaid inflatable chamber at said second extremity, such that said tipinflates after said inflatable chamber at said second extremity.
 16. Aself-propelled device according to claim 1 and further comprising adrilling head attached to a second extremity of said set of seriallyarranged inflatable chambers opposite to said first extremity attachedto said fluid source, such that said drilling head precedes said deviceas it moves along said lumen.
 17. A self-propelled device according toclaim 16 and wherein said drilling head is powered by one of saidinflating fluid, an electric motor and a rotating guide wire. 18-22.(canceled)
 23. A self-propelled device for locomotion through a lumen,comprising: a set of serially arranged inflatable chambers; at least oneconnecting passage providing fluid communication between each pair ofadjacent chambers; a system supplying fluid to a chamber at one end ofsaid set of serially arranged inflatable chambers; and a hollowpassageway running through the central region of said chambers, suchthat said chambers inflate annularly around said passageway, whereinsaid connecting passages are adapted such that said fluid inflates saidset in a serial sequence, from one end to the other end.
 24. Aself-propelled device according to claim 23 and wherein the walls ofsaid chambers surrounding said hollow passageway have a rigidity suchthat said hollow passageway is not compressed by said chambers wheninflated.
 25. A self-propelled device according to claim 24 and whereinsaid central passageway is adapted to contain a threaded element alongat least part of its length, said element being unattached to saidself-propelled device.
 26. A self-propelled device according to claim 25and wherein said threaded element is any one of a guide wire, an opticalfiber or a length of tubing.
 27. A self-propelled device according toclaim 23 and wherein the walls of said chambers enclosing said hollowpassageway apply pressure to said hollow passageway when said chambersare inflated.
 28. A self-propelled device according to claim 27 andwherein said central passageway is adapted to contain a threaded elementalong at least part of its length, such that said chambers grip saidthreaded element when inflated. 29-33. (canceled)
 34. A method ofinserting a guide wire through a lumen, using the device of claim 23,comprising the steps of: (a) inserting said guide wire a predetermineddistance into said lumen; (b) inserting said device into said lumen suchthat it rides on said guide wire; (c) moving said device through saidlumen by sequential inflation of its chambers, until it envelops the tipof said guide wire; (d) advancing said guide wire a furtherpredetermined distance into said lumen; and (e) repeating steps (c) and(d) until said device reaches its target.
 35. The method according toclaim 34, and wherein the walls of at least some of said chamberssurrounding said hollow passageway have a rigidity such that said hollowpassageway is not compressed by said chambers when inflated, such thatsaid device moves through said lumen by gripping the walls of saidlumen.
 36. The method according to claim 34, and wherein the walls of atleast some of said chambers enclosing said hollow passageway applypressure to said hollow passageway when said chambers are inflated, suchthat said device moves through said lumen by gripping said guide wire.37. A self-propelled device for locomotion through a lumen, comprising:a set of two inflatable chambers, both of which expand radially wheninflated and at least one of which also expands axially when inflated;at least one connecting passage providing fluid communication betweensaid two chambers; and a fluid source attached to one of said chambers,wherein said at least one connecting passage is adapted such that fluidfrom said source inflates said two inflatable chambers in a sequence,beginning with said inflatable chamber closest to said fluid source, andending with said inflatable chamber furthest from said fluid source. 38.A self-propelled device according to claim 37 and wherein said fluidsource comprises either one of a fluid supply tube fluid adapted to drawfluid from a supply external to said lumen, a pumping system attached tosaid device and drawing fluid from said lumen, and a closed circuitcontaining said fluid and attached to said device. 39-40. (canceled) 41.A self-propelled device according to claim 37 and wherein said at leastone connecting passage is adapted such that said two inflatable chambersalso deflate in a sequence, beginning with said inflatable chamberclosest to said fluid source and ending with said inflatable chamberfurthest from said fluid source, when said fluid flows out of said twoinflatable chambers.